I decided it was time to present my project to the community and gather some more input. I think it would be awesome if this could become a community project, so please collaborate all you want to, I don't (terribly :P) mind changing anything in "my" design.

Note: this is supposed to be a long-term project and I know it won't happen any time soon, but I do believe this is entirely possible to build even today.

Why a watch?

Watches are technology we depend on a lot in todays life that are also rather small, don't draw a lot of current and are thoroughly researched. Additionally there is a new market for "smartwatches" currently forming that deals with the same problems us biohackers would/will encounter in building this (size, power supply, connectivity) and explores the same possibilities.

Also watches are something that many people wear on their wrist 24/7 (or at least permanently while awake) and are as such great candidates for implants.

What is planned so far?

"features":

implanted in (left) forearm, approximately where a wristwatch is placed, although I guess it would need to sit a bit further up the arm

12 RGB-LEDs (SMD) display time, and keep it precisely (see RTC below)

time synchronization, notifications and general control via mobile phone (bluetooth, see BLE112/3 below)

The problem with just a BLE113 is that the OTA-flashing code is in high-level memory and could easily be rendered useless with a faulty update. If this happened the whole implant would be bricked and would need to be extracted for manual reprogramming.

Therefore it would be better to program a BLE112 to put an ATMega into programming mode and apply the updates. That way a faulty update doesn't brick the OTA code (or device) and can be overwritten.

RTC:

A "smart" RTC can wake up the Microcontroller via the interrupt pin and a timer, saving a lot of power if used effectively. Coupling this with smart software using interrupts on the BLE112 would mean the microcontroller could stay idle for long amounts of time (up to 5 minutes with a permanent clock displaying) saving a lot of power.

LEDs & Accelerometer:

I am aware that LEDs (and RGB leds even more so) consume a lot of power. Even when using only one of the colors and only using one LED at a time the clock would probably be barely sustainable for a full day.

Toggling clock display on and off with accelerometer gestures might be a little hard to implement (and might work against power savings described above) but could lower current drain far enough to compensate that. The simplest form of this would be to just display the clock when the clock is in a specific angled position (tilted towards it's "right" side). Additionally you could add a shaking-unlock or something like that to make it viewable from other angles if needed.

A full-fledged accelerometer chip and a lot of software on the microcontroller could enable the watch to get full-fledged input from the clock, but that will probably need to stay a dream ^^

According to my current plan there will be 12 RGB (Multi-color) LEDs in a circle that work more or less like your everyday-analog watch but that can also show other things (blink in different colors for notifications, rotate colors to just look fancy etc.)

For showing the time every LED would represent 5 minutes, an hour or 12 seconds. It could either display all at the same time (in different colors) or switch between showing each etc. - but these are all software things than can be tested and changed when the actual hardware (or a breadboard demo assembly) has been built.

My question is why do you need LEDs? If you could implant a ring of electrodes on your wrist, they could work similar to an analog clock. This would give you a constant sense of what time it is. In addition, the electrodes could then be adapted for different uses. LEDs are kind of single point orientated.

@ThomasEgi We're talking Bluetooth Low Energy here, it has 3 sleepmodes between 270 uA and 0.5 uA (1uA is the lowest you can go to wake up with internal clock).

Also, like I said above, the LED current can be minimized by using the gyroscopes in a relatively simple manner. I am currently looking into the MPU-6050 Gyroscope and Accelerometer chip which has a "MPU" on board that might be able to do the necessary calculations and comparisons on it's own, which would allow the ATMega to go to lowest sleep mode too (although turning the LEDs off is the much bigger saving anyway).

And the LED stuff really depends on how you use the LEDs and how bright you need to run them, and I don't know how you could test and adjust that reliably before implanting them under skin.

But it brings up another possible way of making a watch; Something that connects with you in some way, like magnets or that (Northpaw? Southpaw?) thing, rather than an actual display, which would let you always know what time it is. Would that kind of thing even be feasible?

Multiple electrodes in a ring (or any other formation) might be a little hard to tell apart, but I'd like to hear @glims opinion on that (it seems he was gonna comment on it).

Anyway, I was going for a visual clock with absolute time interface that is close to today's concept of smartwatches and "regular" wristwatches because the latter are a proven concept that the first successfully improve upon.

Yeah, I'm actually more talking about the size of the implant needed to differentiate between each shock. I don't actually know how large is needed tho I suppose with the right levels you could get a really precise twitch thing set up. There might be a lot of bleed tho.

Then you have the regular shocks. Does the watch only jolt you when you tap it or does it have an accelerometer that knows when you lift your arm to your face or...?

How many regular zaps can your cells take unitl you start distrupting cellular functions?Your cells are little electrical machines, it's important to consider. A few shocks may be fine, but every day, multiple times... maybe there is info out there. I'm travelling so i can't check. I know that electricity will eventually mess your cells up. Anyone who wants to hang out for a few weeks and let me regulalry shock them in the same location and take samples, please contact me :D

@ansamech that depends mostly on the battery, but the rest is much smaller than the circadia, and that is also what I am going for. I won't even think about implanting this as long as it looks as monstrous as the Circadia does, this project has some aesthetic value.

circadia is pretty much the mad-max approach. a properly designed circuit , including battery and bluetooth module can be a lot smaller. i would not recommend led's at all. they eat energy for breakfast and in the end, it's no different from an actual wrist watch since you have to look at it. most energy efficient would be a single electrode pair which uses morse code to tell you the time. given it has bluetooth it can also page text messages etc. a one-electrode implant is pretty much what everyone agreed to be most doable in the last couple of month. i'd be in with helping with the design of it. i already have a fair amount of tests run on electrode drivers. not much of a bluetooth experience here but aside from that i can help.

With a 170mAh battery that means you could receive 100 notifications and check the clock 500 times in a single charging cycle and still have 60mAh over for all the other components (most of which should be in sleep mode the longest time).

i know i wouldnt check a watch 500times a day. i was thinking about charging. obvs inductive is easiest. i was thinking some sort of wrist band with a long lead that you just wear while you sleep at night. therefor never have to worry about it dying.

considering it is blue tooth. could you get it to sync with your phone and do notifications and stuff? (obvs energy draining, just curious if the functionality would work.)

I remember someone talking about electrodes triggering little sensations in your nerves as a means of communication, instead of LED or vibration. @ThomasEgi, is that the same thing you are talking about with the shocks? or are these two diff things?

@ansamech difference between a nice tingling and a shock is just a parameter.

@S0lll0s compare that to 20 days of permanently-on electrode output and this figure includes an atmega cpu running active on 128kHz (and you still have 60mAh charge left). With the output off and the cpu in power-down (watchdog running) i was able to get the circuit down to about 150nA. Low enough to run even on a tiny rechargeable coin (like 20 to 40mAh) battery for quite a long time. Low enough to easily charge with a very simple and small resonating circuit. no need for bulky battery or big resonating coils or charge controllers.Not sure how much power bluetooth will eat. aside from that,the circuit could be kept very simple and small in size.

@ThomasEgi well obviously running just the electrode is more energy efficient, but I'm saying LEDs don't eat too much power to last a day (which would be fine with me).

Anyway, instead of arguing about the output for a few more pages (it's not like we are going to change opinions, I want a smartwatch, you want a controllable electrode), we should maybe continue to discuss the parts of the implant we both need and come up with solutions to shared problems, no?